Allergy and Immunity

Question 1

What is the most common disorder of the immune system?

Answer 1

Allergy (1 in 5 people)

Question 2

What questions should be asked of patients with allergy complaints?

Answer 2

1. How do the symptoms begin?
2. What is the pattern (e.g., perennial, paroxysmal, or seasonal) of the episodes?
3. What is the response to treatment, if any?
4. What are the inducing factors (e.g., inhalants, ingestants, inject ants, exercise, and irritants)?
5. What is the change over time of progression to remission?
6. How severe are the symptoms?

Question 3

What should be included in the allergic history for any person?

Answer 3

I DARE U:

• Insect stings
• Drug or food allergies
• Asthma and anaphylaxis
• Rhinitis
• Eczema
• Urticaria

Question 4

What are the important features of a allergy family history?

Answer 4

• Any atopic disease including asthma, rhinitis, and atopic dermatitis
• History of deaths early in childhood
• Autoimmune diseases
• Angioedema

Question 5

What are the common causes of dyspnea?

Answer 5

10 Ps:

• Pulmonary bronchoconstriction (asthma)
• Pulmonary embolus
• Pneumonia
• Pneumothorax
• Pump failure (congestive heart failure)
• Pericardial tamponade
• Psychogenic
• Poison (carbon monoxide)
• Peak seekers (high altitude)
• Paroxysmal spasm of the vocal cords (vocal cord dysfunction)

Question 6

What are important indoor allergens?

Answer 6

Dust mites, cockroaches, cats, dogs, and moulds

Question 7

What are important outdoor allergens?

Answer 7

Trees, grasses, weeds (ragweed), and moulds

Question 8

List 4 nonspecific components of the innate immune system.

Answer 8

1. Physical barriers (e.g., skin)
2. Complement
3. Polymorphonuclear leukocytes
4. NK cells

(Other innate leukocytes include mast cell, phagocytes, basophils, eosinophils, macrophage)

Question 9

What is the difference between autoimmunity and an autoimmune disease?

Answer 9

Autoimmunity refers to the presence of T cells directed against self. An autoimmune disease is the pathologic organ injury resulting from autoimmunity.

Question 10

Where do T cells mature?

Answer 10

T cells mature in the thymus.

Question 11

Where do B cells mature?

Answer 11

B cells mature in the fetal liver and adult bone marrow.

Question 12

What are the final migration sites for immature T and B lymphocytes?

Answer 12

Secondary lymphoid organs, e.g. Spleen, lymph nodes, intestine (GALT MALT), and peripheral lymphoid tissue

Question 13

What percentage of circulating lymphocytes are T cells?

Answer 13

80%. The majority of the rest are B cells.

Question 14

What is the difference between CD4 and CD8 cells?

Answer 14

T cells bearing CD4 can recognize only those antigens embedded in MHC class II, which is found only on the surface APCs. T cells bearing CD8 can recognize antigens embedded in MHC class I, which is found on all nucleated cells.

(4II = 8 = 8I)

Question 15

Th1 cell function.

Answer 15

Produces: IL2, TNF-β, IFN-γ

Effects: Cell-mediated immunity via activation of macrophage and cytotoxic T cells

Question 16

Th2 cell function.

Answer 16

Produces: IL-4, IL-5, IL-9

Effects: IgE production, Mast cell growth, Eosinophilia

Question 17

B cell function.

Answer 17

• Mature to plasma cell to produce antibody
• Phagocytosis
• Antigen presentation

Question 18

List 5 major Ig isotypes

Answer 18

A, D, E, G, M

Question 19

Most abundant immunoglobin:

Answer 19

IgA is produced in the highest quantities, but IgG has higher measurable levels in blood/serum

Question 20

Where is IgA found?

Answer 20

Most secreted to mucosal surfaces as sIgA.

Question 21

What is unique about IgA and complement?

Answer 21

IgA is the only antibody to activate alternative complement pathway.

Question 22

Where is IgD found?

Answer 22

It is coexpressed with IgM on mature B cells, but its function is not known. It is not a secreted protein.

Question 23

What is the role of IgE?

Answer 23

It is associated with allergy and with immunity to parasites for which it is thought to assist in antibody-dependent cell cytolysis.

Question 24

What is the role of IgG?

Answer 24

• It undergoes somatic mutation with affinity maturation
• a potent opsonin (except IgG4)
• activates the complement
• crosses the placental barrier (as it is small) and provides passive immunity for the newborn

Question 25

How many subclasses of IgG are there?

Answer 25

4 subclasses (IgG1–IgG4).

Question 26

What is the role of IgM?

Answer 26

The antigen receptor found on immature B cells and is the first antibody produced in an immune response. Because one form is pentameric (the other is monomeric), activation of complement is strong.

Question 27

What’s unique about IgM?

Answer 27

Production does not require T-cell help

Does not generate a memory response.

Question 28

What are the 2 types of Ig light chains?

Answer 28

Kappa and Lambda

Question 29

What is the role of immunoglobulin?

Answer 29

Recognition and binding of specific extracellular antigens

• Neutralisation (detoxification)
• Opsonisation

Activation of cells or of the complement-binding system

Question 30

What are the 3 phases of immune response?

Answer 30

Recognition, amplification, response

Question 31

Which cells are APCs?

Answer 31

Dendritic cells

Macrophages

B cells

Question 32

What is the difference between class I and class II MHC?

Answer 32

MHC I:
- Expressed on all cells; presents proteins (usu. viral antigens) synthesised intracellularly (cytosolic/endogenous pathway)

MHC II:
- Expressed on APCs; presents proteins (usu. bacterial antigens) engulfed from extracellular domain and processed (endocytic/exogenous pathway)

Question 33

What are NK cells?

Answer 33

Lymphocytes with receptors for MHC class I, CD 16, CD56